WriteCurrentRegistration方法的问题

Question

package u10a1_ooconsoleregisterforcourse;

import java.util.Scanner;

public class U10A1_OOConsoleRegisterForCourse {

    public static void main(String[] args) {
        System.out.println("Welcome to the Course Registration Program");

        Scanner input = new Scanner(System.in);

        //Courses is an array of course objects
        //see the Course.java source code for members of Course
        Course[] courses = {
            new Course("IT1006", 6),
            new Course("IT4782", 3),
            new Course("IT4789", 3),
            new Course("IT4079", 6),
            new Course("IT2230", 3),
            new Course("IT3345", 3),
            new Course("IT2249", 6)};

        //choice is the number selected by the user
        int choice;
        int totalCredit = 0;
        String yesOrNo = "";

        do {

            choice = getChoice(courses, input);

            switch (ValidateChoice(choice, totalCredit, courses)) {
                case -1:
                    System.out.println("**Invalid** - Your selection of "
                            + choice + " is not a recognized course.");
                    break;
                case -2:
                    System.out.println("**Invalid** - You have already registerd for this "
                            + courses[choice - 1].getCode() + " course.");
                    break;
                case -3:
                    System.out.println("**Invalid** - You can not register for more than 9 credit hours.");
                    break;
                case 0:
                    System.out.println("Registration Confirmed for course "
                            + courses[choice - 1].getCode());
                    totalCredit += courses[choice - 1].getCreditHour();
                    courses[choice - 1].setIsRegisteredFor(true);
                    break;
            }

            WriteCurrentRegistration(courses, totalCredit);

            System.out.print("\nDo you want to try again? (Y|N)? : ");

            yesOrNo = input.next().toUpperCase();
        } while (yesOrNo.equals("Y"));

        System.out.println("Thank you for registering with us");
    }

    //This method prints out the selection menu to the user in the form of
    //[selection number]Course Code (Course Credit Hours)
    //from the courses array one per line 
    //and then prompts the user to make a number selection
    public static int getChoice(Course[] courses, Scanner input) {
        System.out.println("Please type the number inside the [] to register for a course");
        System.out.println("The number inside the () is the credit hours for the course");

        for (int i = 0; i < courses.length; i++)
        {
            System.out.println("[" + (i + 1) + "]" + courses[i].getCode());

        }

        // TO DO
        // loop over the courses array and print out the attributes of its
        //objects in the format of 
        //[selection number]Course Code (Course Credit Hours)
        //one per line
        System.out.print("Enter your choice : ");

        return (input.nextInt());
    }


    //This method validates the user menu selection
    //against the given registration business rules
    //it returns the following code based on the validation result
    // -1 = invalid, unrecognized menu selection
    // -2 = invalid, alredy registered for the course
    // -3 = invalid, No more than 9 credit hours allowed
    // 0 = menu selection is valid
    public static int ValidateChoice(int choice, int totalCredit, Course[] courses) {
        if (choice < 1 || choice > 7) {
            return -1;
        } else if (IsRegisteredBefore(choice, courses)) {
            return -2;
        } else if ((totalCredit + courses[choice - 1].getCreditHour()) > 9) {
            return -3;
        }
        return 0;
    }

    //This method checks the courses array of course object to
    //see if the course has already been registered for or not
    public static boolean IsRegisteredBefore(int choice, Course[] courses) {
        for (int i = 0; i < courses.length; i++) {
            if (courses[choice - 1].getIsRegisteredFor() == true) {
                return true;
            }
        }
        return false;
    }

    //This method prints the current list of registered courses thus far
    //from the courses array separated by , and enclosed inside { }
    //It also prints the total credit registered for thus far
    public static void WriteCurrentRegistration(Course[] courses, int totalCredit) {

        System.out.print("Current course registration:  { ");

        // TO DO
        // loop over the courses array, determine which courses are registered
        //for thus and print them out in the format of
        //{ list of courses separated by , }

        System.out.print("Current course registration:  { " );
        for(Course i : courses) {
            i.getCode();
            if(i.getIsRegisteredFor()) {
                System.out.println(i + ", ");    
            } else {
                System.out.println(" { none } ");
            }
            System.out.println(" }");

            System.out.println("Current registration total credit = " + totalCredit);
        }
    }
}

我一直在玩这种方法几天，我完全迷失了。无论我尝试它只是不正确。这是我编写此方法的第四种不同方式，但没有成功。我也试过

for(int i= 0; i < 4; i++)

我能帮助我解决这个问题。